Photo‐ and Thermoresponsive Dehydration of Spiropyran‐Functionalized Polymer Regulated by Molecular Recognition

• Published in: Macromolecular rapid communications. Vol. 39; no. 1
• Main Authors: Sumaru, Kimio, Takagi, Toshiyuki, Satoh, Taku, Kanamori, Toshiyuki
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.01.2018
• Subjects: Acrylic Resins - chemical synthesis; Acrylic Resins - chemistry; Benzopyrans - chemistry; Coexistence; Cyclodextrin; Cyclodextrins; Cyclodextrins - chemistry; Dehydration; Indoles - chemistry; Irradiation; Isopropylacrylamide; Light irradiation; molecular recognition; Nitro Compounds - chemistry; Photochemical Processes; photoisomerization; poly(N‐isopropylacrylamide); Polymers; Recognition; Spectrophotometry, Ultraviolet; spiropyran; Temperature; spiropyran; photoisomerization; molecular recognition; poly(N-isopropylacrylamide); cyclodextrin
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.201700234

The photo‐ and thermoresponse of poly(N‐isopropylacrylamide) (pNIPAAm) functionalized with spiropyran chromophore is examined with respect to the influence of molecular recognition by cyclodextrin (CD). Characterization in aqueous solutions of spiropyran‐functionalized poly(N,N‐dimethylacrylamide) under coexistence of α‐, β‐, or γ‐CD reveals that β‐CD selectively includes the ring‐closing isomer of the chromophore, which is dominant under light irradiation, while no inclusion is observed for the protonated ring‐opening isomer, which is dominant in the dark before irradiation. As a result, it is shown that the selective inclusion of the chromophore at a polymer side chain is switched by light irradiation. Further, drastic photoresponsive dehydration of spiropyran‐functionalized pNIPAAm is inhibited only by β‐CD out of three examined CDs, demonstrating that the molecular recognition regulates the dehydration of the whole polymer triggered by the photoswitching of the chromophore introduced at only 1 mol% functionalization. Drastic photoresponsive dehydration of a spiropyran‐functionalized polymer induced by the photoisomerization of the chromophores at side chains from a cationic form to a nonionic and hydrophobic form is regulated by the inclusion of hydrophobic isomer by cyclodextrin in a size‐specific manner.